1. Field of the Invention
The invention relates to a method of encapsulating an article and, more specifically, to transfer molding an asymmetric encapsulation for an electronic device, and an asymmetric encapsulated electronic device.
2. Description of the Background
It is well known that electronic devices are sensitive and thus require protection from physical and environmental conditions which may degrade or completely ruin them. Therefore, it is well known in the art to protect electronic devices from these conditions by sealing them with a protective encapsulation material. This "packaging" of the electronic devices protects them from the conditions which may degrade them and allows the devices to be transported and handled, and thus allows them to be easily configured with other components. Several encapsulation methods are known in the art such as under-fill encapsulation (for flip chip applications) and glob topping.
One prior-art method for encapsulating devices is the "transfer-molding" method. Transfer molding is a process through which an encapsulating material, such as a thermosetting material, is caused to flow into a cavity formed by components of a mold. The thermosetting material enters into the cavity and flows over the electronic device that is located within the cavity and is then "cured" so that the resin hardens into a non-flowable state. Traditionally it has been important to control the flow of the material into the cavity for a number of reasons, including: to provide void-free fill over the electrical device, to control the flow of the material so as to not contaminate unwanted areas with the encapsulating material, and to control the flow of the material so as to not cause any wire displacement or other damage to the assembly.
Also, it is well known in the art to use mechanical clamping mechanisms as sealing devices in conjunction with the molding cavity to attempt to contain the thermosetting resin within the cavity prior to curing. However, because mechanical clamps must be applied in a symmetrical fashion, i.e. equal and opposite clamping forces, the configuration of the molds is limited to symmetrical designs.
Therefore there is a need for an improved encapsulation method for transfer molding electronic devices which provides a leak proof sealing mechanism for asymmetric designs while using current equipment and known materials and techniques.